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From: "Dick Rollema"
To: rsgb_lf_group@blacksheep.org
References: <000601c0dbb8$bc424920$1a8c01d4@g4jnt>
Subject: LF: Re: Re: Radiation from loading coil causing difference in current
at top and bottom?
Date: Sun, 13 May 2001 20:54:11 +0200
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To All from PA0SE
Andy, G4JNT wrote:
> But these harmonic currents will upset your readings somewhat - where on a
> scope trace is the RMS value of
> a) the total waveform and
> b) the fundamental ?
>
> The harmonic currents will obviously be out of phase with the harmonic
> voltage, and cannot exit the top of the coil so if they are indeed
entering
> the coil base they must be completing their loop in the fields from the
coil
> itself - the quadrature, non dissipative, H or E fields. Very little
> radiation field will be generated from such a small radiating element,
even
> at harmonic frequencies.
The current into the coil, displayed as the voltage over the resistor in
series with the coil, looked like a pure sinewave. So the harmonics were
only present in the transmitter output VOLTAGE, not in the current into the
coil.
73, Dick, PA0SE
> >The output voltage of the TX was somewhat distorted due to harmonics,
> >showing up as some ripple at the positive and negative peaks of the
> >trace but the zero crossings were at exactly the same points as the
> voltage
> >over the resistor.
> >Thus as far as can be judged from oscilloscope traces voltage and
current
> >at the bottom end of the coil were in phase.